The control of friction and wear of metal mechanical components that are in sliding or rolling-sliding contact is of great importance in the design and operation of many machines and mechanical systems. For example, many steel-rail and steel-wheel transportation systems including freight, passenger and mass transit systems suffer from the emission of high noise levels and extensive wear of mechanical components such as wheels, rails and other rail components. The origin of such noise emission, and the wear of mechanical components may be directly attributed to a number of factors: wheel and rail interaction characteristics; operating conditions including curvature, speed; and rail material strength including hardness.
Mechanical friction at the wheel-rail interaction includes: a) friction on both tangent and curved tracks due to rolling friction on the horizontal interface between wheel and rail and b) curve resistance is the additional resistance in curves due to increased lateral friction forces in curves. The sum of the two effects usually accounts for about 5 to 10% of a train's energy consumption in passenger trains and up to 30% very heavy freight trains.
In a dynamic system wherein a wheel rolls on a rail, there is a constantly moving zone of contact. For purposes of discussion and analysis, it is convenient to treat the zone of contact as stationary while the rail and wheel move through the zone of contact. When the wheel moves through the zone of contact in exactly the same direction as the rail, the wheel is in an optimum state of rolling contact over the rail. However, because the wheel and the rail are profiled, often misaligned and subject to motions other than strict rolling, the respective velocities at which the wheel and the rail move through the zone of contact are not always the same on a tangent section of the railway, causing sliding movement between the wheel and the rail. The sliding movement is more pronounced when fixed-axle railcars negotiate curves wherein true rolling contact can only be maintained on both rails if the inner and the outer wheels rotate at different peripheral speeds. This is not possible on fixed-axle railcars. Thus, under such conditions, the wheels undergo a combined rolling and sliding movement relative to the rails. Sliding movement may also arise when traction is lost on inclines thereby causing the driving wheels to slip. In addition, when the when railcars pass through a curvature, the centripetal force will cause additional friction between the flanges of the profiled railcar wheel and the inside side of the ‘high rail’ of the curvature.
Hence, the requirement for reduction in sliding movement between the railcar wheels and the rail is different between tangent sections and curvature of a railway, between incline and decline of a railway, and a combination thereof.
The magnitude of the sliding movement is roughly dependent on the difference, expressed as a percentage, between the rail and wheel velocities at the point of contact. This percentage difference is termed creepage.
At creepage levels larger than about 1%, appreciable frictional forces are generated due to sliding, and these frictional forces result in noise and wear of components (H. Harrison, T. McCanney and J. Cotter (2000), Recent Developments in COF Measurements at the Rail/Wheel Interface, Proceedings The 5th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems CM 2000 (SEIKEN Symposium No. 27), pp. 30-34, which is incorporated herein by reference). The noise emission is a result of a negative friction characteristic that is present between the wheel and the rail system. A negative friction characteristic is one wherein friction between the wheel and rail generally decreases as the creepage of the system increases in the region where the creep curve is saturated. Theoretically, noise and wear levels on wheel-rail systems may be reduced or eliminated by making the mechanical system very rigid, reducing the frictional forces between moving components to very low levels or by changing the friction characteristic from a negative to a positive one, that is by increasing friction between the rail and wheel in the region where the creep curve is saturated. Unfortunately, it is often impossible to impart greater rigidity to a mechanical system, such as in the case of a wheel and rail systems used by most trains. Alternatively, reducing the frictional forces between the wheel and the rail may greatly hamper adhesion and braking and is not always suitable for rail applications. In many situations, imparting a positive frictional characteristic between the wheel and rail is effective in reducing noise levels and wear of components.
In recent years, significant advancements in lubricant technology have led to the production of special rail lubricants containing friction modifiers that produce “positive friction characteristics” wherein the coefficient of friction increases with the speed of sliding. For example, U.S. Pat. No. 6,135,767 (which is incorporated herein by reference) describes friction modifiers with high or very high positive coefficients of friction; US 2004 0 038 831 A1 (which is incorporated herein by reference) describes a high positive friction control composition with a rheological control agent, a lubricant, a friction modifier, and one, or more than one of a retentivity agent, an antioxidant, a consistency modifier, and a freezing point depressant; and WO 02/26919 (US 2003 0 195 123 A1; which is incorporated herein by reference) describes a liquid friction control composition with enhanced retentivity with an anti-oxidant. The liquid friction control composition may also comprise other components such as a retentivity agent, a rheological control agent, a friction modifier, a lubricant, a wetting agent, a consistency modifier, and a preservative. These friction modifiers are typically solid powders or fine particulates that are suspended in relatively thick fluids. These solid materials enhance friction between a wheel and the rail to promote rolling engagement rather than sliding.
With the development of these new compositions, there is a need for lubricant delivery systems that can accurately and precisely apply such lubricants to the rail. Prior art devices for application of the lubricant or friction modifiers can be classified into two categories: stationary devices on the wayside; and devices mounted on a vehicle.
Stationary devices are usually deployed immediately preceding a location where application is required, the movement of the train tends to move the liquid composition into the area so as to modify the friction on the rail sections and wheel flanges as the train passes. There have been several designs of stationary devices, and apparatus for securing them so as to permit the automatic application of an appropriate composition to the rail when a train passes. In some of these devices, it is the depression of the roadbed that triggers the dispensation of a composition; in others, it is the tripping of a mechanical device, such as a lever or a plunger, by the train's wheels that activates a composition dispensing mechanism. Example of such prior art devices is shown in U.S. Pat. No. 5,641,037. These prior art devices are often mechanically complex and difficult to install and maintain in the field.
Mobile liquid composition delivery devices for lubricating rails, such as the one described in U.S. Pat. No. 5,992,568, may be mounted on a track vehicle, such as a pickup truck (Hi Rail system) equipped with additional flanged wheels.
U.S. Pat. No. 6,578,669 describes a liquid delivery system mounted on a railroad locomotive for applying to a composition to a rail. The system comprises a lubricant path, a reservoir for holding the lubricant, a pump to convey the lubricant along the lubricant path, and a dispensing nozzle mounted to the locomotive above each rail for directing the lubricant onto each rail. However, as drive wheels require good contact with the rail surface, slippage will occur if lubricant is applied in front of any of the drive wheels, and this must be avoided. As locomotives can move in both directions, the delivery system mounted on a locomotive can only be used in an orientation where the active nozzle is behind the driving wheels of the locomotive and this contributes to the complexity of the mechanical systems that already exist on a locomotive. When several locomotives are used in series for pulling heavy freight trains, the nozzle needs to be located behind all driving wheels of the locomotives. The addition or removal of locomotives during use increases the complexity of determining the location of the delivery system within a locomotive consist. Furthermore, a locomotive has limited space for accommodating a liquid reservoir, pump, and delivery systems for applying a liquid composition to a rail system.
Application of liquid compositions within a rail system maybe location dependent, so that a certain liquid compositions may be applied at a certain location of the rail system, applied in different amount at different locations of rail, or different combinations of friction modifiers or friction modifiers and lubricants may be used at different locations of the rail, for example, applied to the top of the rail, or along a side surface of the head of the rail.
Global position system (GPS) has been widely used for locating position on earth. It is well known in the art that navigation systems have been developed, for roadway type vehicles which use a GPS system for determining the approximate location of the vehicle in relation to a street database. By relating the approximate location of the vehicle with information concerning its direction of travel, it is sometimes possible to locate the vehicle on the database